The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Engine control systems typically control the amount of fuel delivered to cylinders of an engine based a base fueling amount and a fuel correction factor. The base fueling amount is determined based on an amount of air drawn into the cylinders and a desired air/fuel ratio. The fuel correction factor is determined based on an input from an oxygen sensor disposed in an exhaust system of the engine.
Some engine control systems diagnose a fuel system fault when the fuel correction factor is outside of a predetermined range. When the fuel correction factor is outside of the predetermined range, the actual air/fuel ratio is typically more lean or more rich than desired. When the engine operates at a lean air fuel ratio, the engine produces increased levels of nitrogen oxide emissions. When the engine operates at a rich air fuel ratio, the engine produces increased levels of hydrocarbon and carbon monoxide emissions.